Planographic printing involves the preparation of a flexible printing plate having water-receptive nonprint areas and water-repellent ink-receptive areas constituting an image to be reproduced. The plate is moistened with an aqueous liquid which is repelled by the image but coats the non-image areas. This renders and maintains the non-image areas of the plate ink free.
In most printing processes, ink is transferred from the image on the printing plate to a copy sheet by an offset blanket to thereby form a reproduction of the image on the copy sheet. The moistening, inking and transfer operations are successively repeated for the production of large numbers of copies.
The aforementioned aqueous liquid is identified as a "fountain solution" in the printing arts. The fountain solution is stored in a container and delivered to the printing plate by a system which includes one or more chrome rollers. The ink is likewise delivered to the printing plate by a series of rollers. Examples of a popular fountain solution are described in U.S. Pat. No. 3,398,002, and U.S. Pat. No. 4,769,072, each of which are incorporated herein by reference. The ink and fountain solutions are continuously fed to the printing plate during the printing process. After a certain number of images have been printed, the printing plate will become "tired", as this term is known and used in the printing art, and the sharpness and clarity of the printing suffers. This can be caused by ambient dust, specks of ink and other foreign substances that accumulate over time.